Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a first image in a sequence of a display screen or portion thereof with transitional graphical user interface showing my new design;

FIG. 2 is a second image thereof; and,

FIG. 3 is a third image thereof.

The broken lines in the figures depict portions of the graphical user interface and form no part of the claimed design.

The outer broken lines illustrating the display screen or portion thereof form no part of the claimed design.

The appearance of the image sequentially transitions between the images shown in FIGS. 1-3. The process or period in which one image transitions to another forms no part of the claimed design. 

CLAIM I claim the ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 